About 12 years ago when I lived in Japan I bought a set of urethane inner tubes for my MTB. They were nearly puncture-proof, and very light. That bike was stolen (when I returned to the US). I'd like to find a set of urethane tubes again but can't seem to locate any. I can't recall who made them but they had a "British" valve for which I had to use a funky adapter to inflate them, so it may have been a British company. The tubes were translucent white in color.
